Sex differences in left bundle branch pacing for cardiac resynchronization therapy: novel procedural insights into pacing lead location.

BACKGROUND: Females have been reported to benefit more than males from biventricular pacing for cardiac resynchronization therapy (CRT). However, whether such sex differences also exist in left bundle branch pacing (LBBP) for CRT and the underlying mechanisms remain unclear. OBJECTIVE: This study aimed to investigate sex differences in LBBP-CRT, with a particular focus on procedural characteristics. METHODS: Patients with heart failure and left bundle branch block who had CRT indications and achieved successful LBBP were retrospectively analyzed. Sex differences in procedural performance and echocardiographic improvement were evaluated. RESULTS: Among 89 patients with successful LBBP, female patients required fewer screw-in attempts (2.0 ± 1.0 vs. 3.2 ± 2.0; P = 0.001), achieved higher rates of left bundle branch trunk pacing (LBTP) (33.3% vs. 9.4%; P = 0.013), and demonstrated shorter paced QRS duration (123.4 ± 14.4 ms vs. 134.3 ± 11.1 ms; P < 0.001) than male patients. At 12-month follow-up, female patients showed greater LVEF improvement (22.3 ± 7.5% vs. 16.5 ± 7.0%; P < 0.001) and a higher super-response rate (75.0% vs. 43.4%; P = 0.003). LBTP was associated with greater LVEF improvement than left fascicular pacing (LFP) in both sexes (P < 0.05). Multivariable logistic regression identified paced QRS duration (OR: 0.94, P = 0.014), LVEDD (OR: 0.87, P = 0.011) and pacing site (LBTP vs. LFP) (OR: 8.32, P = 0.028) as independent predictors of super-response, and mediation analyses suggested that these factors mediated the sex effect on super-response. CONCLUSION: Female patients had a better response to LBBP-CRT, potentially mediated by smaller baseline LVEDD, shorter paced QRS duration, and more frequent LBTP.